The wreckage of John F. Kennedy’s single-engine aircraft shows no evidence so far that it experienced a fire, in-flight breakup or engine problems before it crashed into the Atlantic Ocean and killed Kennedy and two others July 16, the National Transportation Safety Board said in a statement issued yesterday.

The board also said the weather forecast that Kennedy got from the Internet about two hours before his flight began offered no warning of the haze that hung over his route from New Jersey to Martha’s Vineyard. The forecast was for good visual flying conditions with visibility of six to eight miles.

Kennedy’s Piper Saratoga was on approach to Martha’s Vineyard when it made a series of turns and then fell from the sky at 9:41 p.m., killing Kennedy, his wife, Carolyn Bessette Kennedy, 33, and her sister, Lauren Bessette, 34.

The board did not address whether Kennedy, 38, might have become disoriented while flying over the ocean on a nearly moonless night in thick haze. Normally in crash investigations, the board first eliminates mechanical or structural causes before considering pilot error.

The board said that Kennedy had more than 300 hours of flying time, somewhat more than originally reported. However, pilots said that 300 hours would have left Kennedy at an experience level when pilots often become overconfident and are not sufficiently seasoned to recognize dangerous situations.

The board’s statement said that about 75 percent of the aircraft had been recovered from the ocean floor by the Navy salvage ship USS Grasp. That included 80 percent of the left wing, 60 percent of the right wing, the engine and propeller and the cockpit instrument panel.

“Examination of the wreckage by NTSB investigators has revealed no evidence of an in-flight breakup or fire, and no indication of pre-impact failure to the airframe,” the statement said.

The statement noted that the engine had been examined by manufacturer Textron Lycoming and the propeller had been examined by manufacturer Hartzell Propeller Inc. under the supervision of NTSB investigators. “No evidence was found during the examinations of conditions that would have prevented either the engine or propeller from operating,” the statement said. The propeller showed signs of “rotational damage,” the board said, indicating that it was turning when it hit the water.

The board said the wreckage also included a small voice-recording device that investigators had hoped might contain some last-minute sounds that could help explain the crash, but it was destroyed upon impact. Small aircraft normally do not have voice recorders, and those that are installed are not crash-protected like airliner recorders.

The board indicated that it will pursue the question of whether Kennedy received proper weather advice. The weather forecast assured pilots of good visual flying conditions, and no special reports warned pilots of any significant meteorological conditions.

“However, pilots who had flown over Long Island Sound that evening reported after the accident that the in-flight visibility over the water was significantly reduced,” the statement said. “Interviews with those pilots will continue.”

The statement said board investigators will examine the plane’s recovered global positioning satellite equipment and its radios. Investigators will continue to document Kennedy’s flight time and training, complete its radar data analysis of the flight and collect weather readings for the time of the flight, the statement said.